1. Field of the Invention
The present invention relates to an air conditioner for a vehicle, which includes an air conditioning case having therein a first air passage and a second air passage and introduces the inside air and the outside air into the first air passage and the second air passage, respectively.
2. Description of Related Arts
Conventionally, an air conditioner for a vehicle, of this type, has been disclosed in JP-A-5-124426. In an air conditioning case of this air conditioner for a vehicle, there are formed an inside air inlet and an outside air inlet on one end side and formed on the other end side a foot air outlet, a defroster air outlet and a face air outlet.
In the air conditioning case, there is provided a partitioning plate which partitions an interior thereof into a first air passage extending from the inside air inlet to the face air outlet and the foot air outlet and a second air passage extending from the outside air inlet to the defroster air outlet.
Further, in the both air passages, there are provided a heating heat exchanger, a bypass passage bypassing the heating heat exchanger, and air mix doors. The air mix doors are constructed such that the door on the first air passage side and the door on the second air passage side are integrally provided on a single rotary shaft rotatably provided over the both air passages.
When any one of a face mode, a bi-level mode and a foot mode is selected as the air outlet mode, if the inside/outside air mode at this time is an inside air circulation mode, the inside air is introduced into the both air passages. On the other hand, if the inside/outside air mode at that time is an outside air introduction mode, the outside air is introduced into the both air passages. Also, when a defroster mode is selected as the air outlet mode, the outside air is introduced into the both air passages.
When a foot/def mode is selected as the air outlet mode, the inside/outside air mode is set to a two-layer mode in which the inside air is introduced into the first air passage and the outside air is introduced into the second air passage. By using this two-layer mode, since the interior of the passenger compartment is heated by the inside air having been already heated, the heating performance is enhanced. Further, since the outside air having low humidity is blown out into the windshield, the frost prevention performance of the windshield is enhanced.
In contrast to the above air conditioner for a vehicle, there has been disclosed an apparatus wherein the air mix door on the first air passage side and the air mix door on the second air passage side are independently rotated in JP-A-62-29411.
However, as a result of the present inventors' studies and examinations, it turns out that, in the apparatuses disclosed in JP-A-5-124426 and JP-A-62-29411, when the two-layer mode in which the inside air is introduced into the first air passage and the outside air is introduced into the second air passage is set, since the temperature difference (hereinafter referred to as "upper/lower temperature difference") between the temperature of the air blown out into the feet of the passenger and the temperature of the air blown out into the windshield varies due to the temperature of the outside air, the passenger may feel uncomfortable depending on the temperature of the outside air introduced at that time. The reason will now be described.
First, in the apparatus disclosed in JP-A-5-124426, as mentioned above, the air mix door on the first air passage side and the air mix door on the second air passage side are both rotated integrally with each other. Accordingly, when the interior of the passenger compartment is set to a predetermined set temperature, the air mix doors on both the first and second air passage sides have the same predetermined opening degrees.
Here, since the inside air is introduced into the first air passage, the temperature of the air blown out from the foot air outlet to the feet of the passenger through this first air passage has no relationship with the temperature of the outside air. However, since the outside air is introduced into the second air passage, the temperature of the air blown out from the defroster air outlet to the windshield through this second air passage varies in correspondence with the temperature of the outside air.
Accordingly, in the case the air mix doors are rotated to the predetermined opening degrees, even if the upper/lower temperature difference when the temperature of the outside air is a predetermined value is comfortable for the passenger, the temperature of the air blown out to the windshield becomes higher when the temperature of the outside air is higher than the predetermined value, despite the temperature of the air that blown out to the feet of the passenger does not vary, the upper/lower temperature difference becomes smaller and as a result the face portion of the passenger may be flushed.
When the opening degrees of the air mix doors is so adjusted as to decrease the air temperature to prevent the face portion from being flushed, since both of the air mix doors for the air passages are moved together, the temperature of the air blown out to the feet of the passenger may be inconveniently lowered, and as a result a cool feeling due to the cool air is given to the feet of the passenger.
Also, when the upper/lower temperature difference is tuned so as to be an appropriate value in a mode where the inside or outside air is introduced into each of the first and second air passages, this temperature difference, since the temperature of the air blown out to the windshield is lowered in accordance with a decrease in the temperature of the outside air introduced into the second air passage when the inside/outside air mode is set to the two-layer mode, the upper/lower temperature difference becomes larger, and the passenger may feel uncomfortable.
Also, in the apparatus in JP-A-62-29441, since the passenger manually adjusts the temperatures of the conditioned airs in the first and second air passages, there is no description of the method against the variation in the upper/lower temperature difference due to the change in the temperature of the outside air in an automatic air conditioner in which the temperature of the conditioned air is automatically controlled. As a result of studies and examinations by the inventors, it turns out that, when the opening degree of the air mix door provided in the second air passage is set to a certain value, the temperature of the outside air decreases, and the upper/lower temperature difference becomes larger.